Osamu Honda Hiroyuki Ohsaki Makoto Imase Kazuhiro Matsuda Ring-Based Virtual Private Network Supporting a Large Number of VPNs. 33 2007 conf/icn/2007 ICN http://doi.ieeecomputersociety.org/10.1109/ICN.2007.78 db/conf/icn/icn2007.html#HondaOIM07